At 12/26/2012 11:02 AM, Kamezawa Hiroyuki Wrote: > (2012/12/24 21:09), Tang Chen wrote: >> From: Wen Congyang <wency@xxxxxxxxxxxxxx> >> >> memory can't be offlined when CONFIG_MEMCG is selected. >> For example: there is a memory device on node 1. The address range >> is [1G, 1.5G). You will find 4 new directories memory8, memory9, memory10, >> and memory11 under the directory /sys/devices/system/memory/. >> >> If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup >> when we online pages. When we online memory8, the memory stored page cgroup >> is not provided by this memory device. But when we online memory9, the memory >> stored page cgroup may be provided by memory8. So we can't offline memory8 >> now. We should offline the memory in the reversed order. >> > > If memory8 is onlined as NORMAL memory ...right ? Yes, memory8 is onlined as NORMAL memory. And when we online memory9, we allocate memory from memory8 to store page cgroup information. > > IIUC, vmalloc() uses __GFP_HIGHMEM but doesn't use __GFP_MOVABLE. > >> When the memory device is hotremoved, we will auto offline memory provided >> by this memory device. But we don't know which memory is onlined first, so >> offlining memory may fail. In such case, iterate twice to offline the memory. >> 1st iterate: offline every non primary memory block. >> 2nd iterate: offline primary (i.e. first added) memory block. >> >> This idea is suggested by KOSAKI Motohiro. >> >> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx> > > I'm not sure but the whole DIMM should be onlined as MOVABLE mem ? If the whole DIMM is onlined as MOVABLE mem, we can offline it, and don't retry again. > > Anyway, I agree this kind of retry is required if memory is onlined as NORMAL mem. > But retry-once is ok ? I'am not sure, but I think in most cases the user may online the memory according first which is hot-added first. So we may always fail in the first time, and retry-once can success. Thanks Wen Congyang > > Thanks, > -Kame > >> --- >> mm/memory_hotplug.c | 16 ++++++++++++++-- >> 1 files changed, 14 insertions(+), 2 deletions(-) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index d04ed87..62e04c9 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -1388,10 +1388,13 @@ int remove_memory(u64 start, u64 size) >> unsigned long start_pfn, end_pfn; >> unsigned long pfn, section_nr; >> int ret; >> + int return_on_error = 0; >> + int retry = 0; >> >> start_pfn = PFN_DOWN(start); >> end_pfn = start_pfn + PFN_DOWN(size); >> >> +repeat: >> for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) { >> section_nr = pfn_to_section_nr(pfn); >> if (!present_section_nr(section_nr)) >> @@ -1410,14 +1413,23 @@ int remove_memory(u64 start, u64 size) >> >> ret = offline_memory_block(mem); >> if (ret) { >> - kobject_put(&mem->dev.kobj); >> - return ret; >> + if (return_on_error) { >> + kobject_put(&mem->dev.kobj); >> + return ret; >> + } else { >> + retry = 1; >> + } >> } >> } >> >> if (mem) >> kobject_put(&mem->dev.kobj); >> >> + if (retry) { >> + return_on_error = 1; >> + goto repeat; >> + } >> + >> return 0; >> } >> #else >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html